spark plugs
 

Hi, just found out this block had the wrong plugs ac delco number .CR43TS suppose to be MR43T according to the good book/manual what would be the difference between the two ? heat , depth ? should I stay with the CR . engine is a 454 bravo. thank you.

Are they ngk. Possibly copper core resistor and ts would be tapered seat with 5/8 hex and extended seat. If it's not an ac delco plug I'm not a 100 % on the 43 being heat range.

Should be able to do a cross reference. I've always used nothing but the ac mr43t on marine NA but a number of other plugs are used also.

Heat range can be your biggest enemy and depth off threads. Mr43t's are close to 5/8" from top of seat to the bend of tip

Is it just a std carbed 454 mag

yes both ac delco

Their pretty much the same plug, M is always spec for Marine for nickel outer jacket, differences

CR - Hex 5/8, gap .044, nickel chrome alloy housing, Cost 1.99
MR - Hex 13/16, gap .040, nickel alloy housing, Cost 2.69

There u go. I kinda messed up on some wording as I was driving down the road but you got what u needed. Although strange I've never used that plug. Provably the less expensive plug looked enticing even though it's probably the least expensive thing we do.

On the flip side of things is there a said rule of thumb on heat range go down as you go up in power. I've used the ac43 from stock 454 - 330/365/480/675 hp without issues. What's recommended for a sc 900 hp plus build?

I Dont mean to dirty up the OT however while in the topic....

NGK BR6FS gapped at .40 and on some apps depending which 454 --- BPR6EFS gapped at .45

just saying as the OP never said which 454 he had but to prove not all 454 took the same plugs nor parts cause I know doing this everyday. OP side shows a 1998 Crownline 266 so a guess which 454 he has. Working on boats one has to take the guess work out of the mix completely. Posting plugs numbers not knowing exactly what one has can be an failure in the making --- a huge mistake of advice.

Keep in mind it is important to post exactly what one has and engine serial number. Why because it is a dart board for proper parts. I can not stress that enough. Never assume what was in there to begin with being correct in the FIRST PLACE, My self can care less what the last guy whom work on the boat did because it can be wrong with used boats. Actually not uncommon

BPR6EFS is a projected nose tip and extended reach plug. All spark plugs are recommended per app only not across the aboard.

number 29 in the parts script below from the link and even pic links of the plug. One can see the difference of a projected tip and long reach vs non

MerCruiser 7.4L Bravo (MPI) (Gen. VI) GM 454 V-8 1998-2000 Distributor & Ignition Components Parts

c=commercial
m=marine

43 is the heat range

ts is an extended tip vs the t

there are no mR43ts's for some reason, so for those like me that like to have the slightly longer tip we get the cr43ts's.

hope that makes sense.

and the mag 454 MPI for 1998 different than the 1998 454 MPI and both are GEN VI

MerCruiser 454 Mag MPI Bravo (Gen. VI) GM 454 V-8 1998 Distributor & Ignition Components Parts

I know some if not all gen VI big blocks using oval port heads use a long reach plug vs the old short MR43's

So in reality no one knows for sure what year engine, model etc he is referring to. I get the avitar show 98 crowine but...
His question was the difference btwn the two plugs stated and his manual stated mr43t. Is it a generic manual or is it possible he doesn't have original engine? Just saying! �� We do know it's a 454 carbed engine just not a 100% certain on year. I've had a boat with 3 different gens and size engines so it would be like going to Napa looking for plugs for a 76 escort although you have a modified 302 crammed in it. You'd likely leave with 4 incorrect plugs.

just putting this out there Merc did not make any carb engines for big blocks in 1998 nor in 1997 - their last carb big block was 1996 - 454 and no 502 carb engines for 1996. info is for black production side.


1997 454 was TBI and MPI
1998 454 was MPI and I believe last of the TBI s

the L 29 / 454 used the long reach plugs

It's good info bup. The simple days are gone. Honestly I like all the pre early ninety merc stuff. Probably cause it's what I worked on the most and could do most anything with a blindfold if I had to. Maybe a quick peek for timing. Lol... I get it though things change for better or worse.

keep in mind you have to account for replacement long block engines, where mine got screwed up, no plug #'s came with engine, so what we had been using is what we used, wrong for about 4 years, until pulled one engine down saw the plugs were way short...but seemed to run fine, but never saw over 4000 either

4 years.... at least they don't owe you anything.

I just went this route today, but wasn't sure about the gap size(went with NGK's BR6FS plugs). I went onto NGK's website, but their gap recommendation is set at .032, but set them at 35. I keep reading 40, but for the MR43TS.
How much of a big deal will it make, .040 vs .035?

MR43TS are available here, but as someone posted a link, they also cross reference to NGK BR6FS(which is why I went with NGK. Can anyone cite references on the correct gap?

Thanks

Your engine serial number is ??? Thats the way all parts and procedures goes by for the marine end. regardless what year the hull is.

I have the latest NGK app guides as well for all powersports. NGK has not had a new guide out in about 3 or 4 years. The new guide came out past couple of months.

First few begin with OK179, that’s how I came about the NGK crossref number.

need all of it - as to look it up thru Merc. this will tell me year built and exactly the complete build plus hp and so on of your engine. It will give me the exact plug what Merc recommends as well. Anyways no big deal if not.

PM sent

.....mouse turds

And still waiting

Ill run it thru when I get a chance. my paying customers come first. Freebie stuff is when I get around to it. Sorry ,man and the super bowl for the whole day. Really do not know how to take your post as I was to jump right to it ? or at my convenience ? .

Not a problem, I understand. Didn’t mean anything by it.

But the mouse turds guy, i Can’t explain, what hats about

Br6fs .040

Just an FYI

I called NGK technical support, I provided my engine make model, and confirmed the the correct NGK sparks plugs for 502 8.2 Liter are the BR6FS Plugs. They should be gaped at .032 from the factory(should), but they need to be gapped at .040 for my setup.

NGK has a customer support line, anyone can call for Free and obtain all the information you need.:riding:

Champion spark plugs Technical Support

1.800.325.8886
Monday – Thursday: 7:30 a.m. – 4:30 p.m. (CST)
Friday: 7:30 a.m. – 4:00 p.m. (CST)

Manual 23

^^^ will have to add as important info, Even thou the manual above was written 22 years ago and some of it is correct - but things do change overtime.. Hence why it should be looked at for the current updates from the OEM's and the spark plug manu's.

A good example of this was the updated spark plugs for the Merc ECM 555 engines thru OEM service bulletin, Plus the other thing was the Merc 496's original came with Denso spark plugs. Well that changed very quickly as well.

Another example is the listing above post 31 - for champion listing RV15YC4 - but currently RV9YC is the recommended Champion spark plug cross referenced in some of the marine big blocks, Again that manual was written 22 years ago not all always applies

The long reach plugs are for the 7.4 L MPI L- 29 engines as I mentioned before in a past post.